Proteins have a distribution of structures accessible to their native state in solution. This collection of structures is narrowed in a high resolution crystal structure due to the physical constraints imposed by the crystal lattice. Conformers from morphologically different crystal differ according to the availability of energetically favorable contacts within a specific lattice packing arrangement. To explore alternate conformations available to a protein for molecular packing in polymorphic crystal cells, four 102 ps MD simulations of three different wildtype BPTI crystal structures were calculated. Despite the different starting structures and initial velocity assignments, the RMS backbone fluctuations were more similar and more consistent among the MD simulations than were the corresponding crystallographic B-factors. Many dihedral conformations and hydrogen bonds that were not common in the crystal structure analyses were common among these simulations, although no one simulation identified the conformational space available to the other protein crystal forms. To probe the consequences of insufficient sampling, structures from a stable 20 ns simulation were characterized and compared to those from the shorter simulations. Despite the unusually long simulation time, the protein was similar to the crystal structure, with RMS deviations between the average structure and the starting crystal structure of 1.0 and 1.4 angstroms, for the protein backbone and all heavy atoms, respectively. Sixteen out of the eighteen dihedral conformations that were specific for the other protein crystal forms and all of the crystal form-specific hydrogen bonds were found in this longer simulation. Thus, the structural differences among the crystal forms are thermally accessible to a single crystal model. The UCSF Computer Graphics Laboratory was used to set up, monitor and analyze the molecular dynamics simulations in this study.